package org.apache.lucene.index;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/** Consumes doc & freq, writing them using the current
 *  index file format */

import java.io.Closeable;
import java.io.IOException;

import org.apache.lucene.util.IOUtils;
import org.apache.lucene.util.UnicodeUtil;
import org.apache.lucene.index.FieldInfo.IndexOptions;
import org.apache.lucene.store.IndexOutput;

final class FormatPostingsDocsWriter extends FormatPostingsDocsConsumer implements Closeable {

    final IndexOutput out;
    final FormatPostingsTermsWriter parent;
    final FormatPostingsPositionsWriter posWriter;
    final DefaultSkipListWriter skipListWriter;
    final int skipInterval;
    final int totalNumDocs;

    boolean omitTermFreqAndPositions;
    boolean storePayloads;
    long freqStart;
    FieldInfo fieldInfo;

    FormatPostingsDocsWriter(SegmentWriteState state, FormatPostingsTermsWriter parent) throws IOException {
        this.parent = parent;
        out = parent.parent.dir.createOutput(IndexFileNames.segmentFileName(parent.parent.segment, IndexFileNames.FREQ_EXTENSION));
        boolean success = false;
        try {
            totalNumDocs = parent.parent.totalNumDocs;

            // TODO: abstraction violation
            skipInterval = parent.parent.termsOut.skipInterval;
            skipListWriter = parent.parent.skipListWriter;
            skipListWriter.setFreqOutput(out);

            posWriter = new FormatPostingsPositionsWriter(state, this);
            success = true;
        } finally {
            if (!success) {
                IOUtils.closeWhileHandlingException(out);
            }
        }
    }

    void setField(FieldInfo fieldInfo) {
        this.fieldInfo = fieldInfo;
        omitTermFreqAndPositions = fieldInfo.indexOptions == IndexOptions.DOCS_ONLY;
        storePayloads = fieldInfo.storePayloads;
        posWriter.setField(fieldInfo);
    }

    int lastDocID;
    int df;

    /** Adds a new doc in this term.  If this returns null
     *  then we just skip consuming positions/payloads. */
    @Override
    FormatPostingsPositionsConsumer addDoc(int docID, int termDocFreq) throws IOException {

        final int delta = docID - lastDocID;

        if (docID < 0 || (df > 0 && delta <= 0))
            throw new CorruptIndexException("docs out of order (" + docID + " <= " + lastDocID + " ) (out: " + out + ")");

        if ((++df % skipInterval) == 0) {
            // TODO: abstraction violation
            skipListWriter.setSkipData(lastDocID, storePayloads, posWriter.lastPayloadLength);
            skipListWriter.bufferSkip(df);
        }

        assert docID < totalNumDocs : "docID=" + docID + " totalNumDocs=" + totalNumDocs;

        lastDocID = docID;
        if (omitTermFreqAndPositions)
            out.writeVInt(delta);
        else if (1 == termDocFreq)
            out.writeVInt((delta << 1) | 1);
        else {
            out.writeVInt(delta << 1);
            out.writeVInt(termDocFreq);
        }

        return posWriter;
    }

    private final TermInfo termInfo = new TermInfo(); // minimize consing
    final UnicodeUtil.UTF8Result utf8 = new UnicodeUtil.UTF8Result();

    /** Called when we are done adding docs to this term */
    @Override
    void finish() throws IOException {
        long skipPointer = skipListWriter.writeSkip(out);

        // TODO: this is abstraction violation -- we should not
        // peek up into parents terms encoding format
        termInfo.set(df, parent.freqStart, parent.proxStart, (int) (skipPointer - parent.freqStart));

        // TODO: we could do this incrementally
        UnicodeUtil.UTF16toUTF8(parent.currentTerm, parent.currentTermStart, utf8);

        if (df > 0) {
            parent.termsOut.add(fieldInfo.number, utf8.result, utf8.length, termInfo);
        }

        lastDocID = 0;
        df = 0;
    }

    public void close() throws IOException {
        IOUtils.close(out, posWriter);
    }
}
